The invention relates generally to coatings and, more particularly, to apparatus and methods for testing the adhesion of coatings.
Surface treatments are used to alter the mechanical, electrical, thermal, optical, corrosion resistance, and wear properties of a component. Diffusion techniques generally alter the surface of the component, whereas deposition techniques cover the surface of the component with a solid material to accomplish the above. Deposition techniques include electroplating, physical vapor deposition, and chemical vapor deposition. Physical vapor deposition (xe2x80x9cPVDxe2x80x9d) coatings, for example, are generally formed by removing atoms, ions, and/or molecules from a source and depositing the atoms on a surface of the component. Because deposition techniques result in a coating on the component surface, the altered properties of the component generally depend on complete adhesion of the coating on the surface of the component.
Testing of adhesion by indentation techniques and scratch techniques damage the coating and, thus, affect the altered property of the component. Furthermore, these techniques only test the adhesion of the coating at or near the indentation or scratch. A nondestructive technique disclosed in U.S. Pat. No. 5,454,260 attempts to overcome this problem by using a supersonic jet of water directed towards the coating. In the disclosed method, the supersonic jet of water is pre-calibrated to be slightly below the intensity that causes failure of the coating. The supersonic jet of water is then directed towards one or more sites on the coating. If the coating at the sites do not fail after impingement by the supersonic jet of water, adhesion of the coating is determined to be sufficient. One problem with the disclosed method is that it tests adhesion of the coating only at discrete sites. Another problem is that diameter of the supersonic jet of water limits testing of small components and makes testing of large components impractical.
Thus, there is a need to overcome these and other problems of the prior art and to provide an apparatus and method for adhesion testing of coatings. The present invention, as illustrated in the following description, is directed to solving one or more of the problems set forth above.
In accordance with an embodiment of the present invention, an apparatus for adhesion testing is disclosed. The apparatus includes a converter and a vibratory horn coupled to the converter, the vibratory horn having a tip end. The apparatus further includes a liquid medium in which the tip end is submerged to generate a cavitation field in the liquid medium. A stage is adapted to move a component having an adhered coating on at least a portion of the component though the cavitation field to locate areas of the coating that are poorly adhered.
Alternatively, a stage may be adapted to move the vibratory horn relative to a surface of a component to locate areas of a coating on the surface of the component that are poorly adhered.
In accordance with another embodiment of the present invention, a method for adhesion testing is disclosed. The method include submerging a tip end of a vibratory horn in a liquid medium and operating a converter, coupled to the vibratory horn, at a frequency and an amplitude to generate a cavitation field within the liquid medium. The component having a coating is moved such that the coating passes through the cavitation field. Areas of the coating that are poorly adhered to the component are located by removing the areas of the coating that are poorly adhered, while not removing areas of the coating properly adhered to the component.
In accordance with another embodiment of the present invention, a method for adhesion testing is disclosed. The method includes submerging a tip end of a vibratory horn in a liquid medium and operating a converter, coupled to the vibratory horn, at a frequency and an amplitude to generate a cavitation field within the liquid medium. The vibratory horn is moved relative to a component having a coating such that a first portion of the coating is in the cavitation field. In this manner, areas of the coating that are poorly adhered to the component are located by removing the areas of the coating that are poorly adhered, while not removing areas of the coating properly adhered to the component.